<!DOCTYPE html>
<script>
onload = () => {
  outerDiv.scrollTop = 300;
  innerDiv.scrollTop = 400;
}
</script>
<div style="height: 300px; overflow-y: auto;" id="outerDiv">
  <div style="height: 300px;"></div>
  <div style="height: 400px; overflow-y: auto;" id="innerDiv">
    <div style="height: 800px; width: 300px; background: green;"></div>
  </div>
</div>
